1. Field of the Invention
The invention relates to a powered actuator for displacing the toggle, handle or other operator of a switch, such as a breaker for an electric power distribution circuit. The actuator includes a driver operable to move a shaft between extended and retracted positions, a couple defining a receptacle that engages over the toggle or handle of the switch, and a mechanism interconnecting the shaft with the couple such that changes in position in the shaft induce changes in position in the toggle or handle via the couple.
The driver can comprise a linear induction motor extending and/or retracting an associated motor shaft in response to control signals, for example from a remote controller operated either manually or by programmable devices. Other forms of drivers are also possible. The mechanism includes a pair of cam members, each defining an enclosed slot. An abutment member is carried by the motor shaft and has portions extending into the enclosed slots. A pair of links are pivotally connected, respectively, to the cam members and to the couple. Each cam member has a mounting-hole spaced from the enclosed slot, and the cam members are pivotally mounted to a stationary support structure for pivoting about a fixed axis that extends through the mounting-holes.
Motion of the abutment member in the enclosed slots causes the cam members to pivot. This pushes or pulls the rigid links, displacing the toggle or handle via the couple and operating the switch.
2. Prior Art
Powered switch actuation devices are known in power distribution applications, for example as means to switch a load circuit between power grids in response to signals sent by a remote controller. The controller can be operated manually or can be responsive to a programmable device. Such switch control devices may be intended to operate heavy duty switches rated for switching formidable loads, such as loads in the hundreds or thousands of volts at thousands of amps. However the devices themselves advantageously are operated at considerably lower power levels, for example, 110 VAC at 12 A, and can be controlled by switching means triggered by signals of much lower power still.
Switch control devices may be configured in single switch configurations (e.g., as in FIGS. 1 and 2 herein), or in plural switch configurations. A dual configuration intended to switch a load circuit from one line circuit to another line circuit is commonly known as a transfer switch, and an example is disclosed in U.S. Pat. No. 5,274,206, granted Dec. 28, 1993, entitled "SPRING CHARGING MECHANISM FOR CIRCUIT BREAKERS AND TRANSFER SWITCHES," by inventor Stanislaw A. Milianowicz, the disclosure of which is hereby incorporated. In a typical application, a transfer switch switches a load circuit from a primary power line or grid to an auxiliary one, or back again. Single switch configurations having one or more poles can be arranged in gangs with other single or multiple switches and actuators for more complex switching schemes, for example where related loads or lines are switched in a coordinated manner.
More generally, single switch configurations are useful for operating a switch via a remote controller and/or for operating the toggles or handles of large circuit breakers. A circuit breaker for high power loads may require 150 to 300 lbs (70 to 140 kg) of force to displace, which force is perhaps too much to manually displace safely without some type of mechanical advantage.
Switch actuators advantageously provide good mechanical advantage for operating the toggle or handle. An important consideration is the manner in which the actuator is powered or driven, and how the driving force is coupled to the toggle or handle. Advantageously, a switch control or actuation device should not unduly complicate the apparatus, should involve a minimal expense to make and use, and should be durable and long-lived. Additionally, the actuator should be compact because space on power distribution panels is relatively valuable.
The concept of mechanical advantage or leverage is to couple a driving stroke to a driven stroke so as to convert the applied force of a relatively longer driving stroke to a higher force over a shorter driven stroke, i.e., the operative displacement of the toggle or handle. Preferably, the resultant force is several times greater than the applied driving force. Known switch control devices are disadvantageous in that they cannot amplify the applied driving force by a significant factor or in an optimal manner. Amplification of the force produced by the actuating driver is desirable because it reduces the electric power level needed to operate a given switch.
It is generally necessary in a lever arrangement for increasing force, to provide a driving stroke that is proportionately longer than the driven stroke, by an amount corresponding to the factor by which the force is to be multiplied. Various lever arrangements are conceivable for operating a switch. However, it would be advantageous if the means or mechanism that amplifies the applied driving force could be kept small, durable, inexpensive and uncomplicated. In connection with actuator mechanisms for switches, it is important that the mechanism have only a small extension in a direction perpendicular to the plane of the panel on which the switch is mounted.
Conventional drivers or motors for switch actuators include rotary electric motors turning either a threaded drive-shaft coupled with a driven nut or a crank pushing and pulling a lever, and pneumatic or hydraulic actuators. According to one aspect of the invention, a linear induction motor is used as the driver of a switch actuator. A linear induction motor provides a high speed straight-line action similar to that of a hydraulic or pneumatic actuator without the complications of the associated hydraulic and pneumatic circuits. According to another aspect, an improved mechanism is coupled to the motor for amplifying the driving force of the motor, providing a reasonably sized, reasonably priced switch actuator that is compact and durable.